Salim Ahmed Hamdan never planted a bomb, never took a hostage, never wielded a box cutter, never fired a weapon in anger, and never planned an attack of any kind.

What he is alleged to have done, according to his US military commission charge sheet, is work as Osama bin Laden's driver in Afghanistan.

So how could military prosecutors at Guantánamo Bay, Cuba, charge him with being a terrorist and war criminal? The answer boils down to a single word: conspiracy.

The same legal approach that helped put mafia dons, capos, and associates behind bars in America is at the center of US military efforts to prosecute suspected Al Qaeda members for war crimes.

But now in the wake of the US Supreme Court's decision in the Hamdan case invalidating the military commission process, it is unclear to what extent military prosecutors can continue to use conspiracy as a war crimes charge.

The Bush administration is asking Congress to simply pass a law recognizing conspiracy as a war crime.

But some legal experts warn that the law of war is a reflection of both domestic and international standards that should not be watered down unilaterally by US lawmakers. They say such a move would further undermine US standing as a champion of human rights and set the stage for another major defeat in the courts for President Bush.

"This is just contempt for the court's opinion," says George Fletcher, a professor at Columbia Law School who authored a friend of the court brief in the Hamdan case that first raised the conspiracy issue. "If Congress says we can go around it, that is just crazy. They don't understand what they are doing."

In its June opinion, a five-member majority of justices struck down the military commissions at Guantánamo because they did not comply with the requirements of the Uniform Code of Military Justice and Common Article 3 of the Geneva Conventions. That part of the decision addressed what the high court viewed as fatal procedural defects – including a rule allowing the exclusion of a defendant from parts of his own trial.